If it’s the first weekend in May, it must be Marvel superhero time. Spider-Man and its two sequels, plus both Iron Man movies and the Wolverine prequel, have all kick-started the summer movie season in burly style. Now it’s Thor‘s turn. The Norse god — first Marvelized in a 1962 comic book — introduces what is conceived as a zillion-part movie series about the Avengers team of Marvel stalwarts. Captain America, impersonated by Chris Evans, gets his own starring chapter in July; another Avenger, the James Bondian Nick Fury (Samuel L. Jackson), comes next year.

Like its namesake, Thor is big, blond-bland, handsomely put together and a little musclebound. Played by an Aussie Adonis named Chris Hemsworth, whose looks and demeanor suggest a young, airbrushed Nick Nolte, Thor sports a permanent scowl — perhaps because, in the alternate universe of the movie business, he had his, oh, thunder stolen by the carjackers of Fast Five, which jumped the traditional opening date of the Hollywood blockbuster season by a week and proved a popular smash. So this weekend Thor faces two daunting challenges: to vanquish his enemies in mythological Norway and modern-day New Mexico, and to top Fast Five‘s $86.2-million box-office haul.

Early on, that seems an impossible task, given the heavy weather of the first part of the film. Set in the mists of ancient Asgard — the home of Thor, his brother Loki (Tom Hiddleston) and their regal dad Odin (Anthony Hopkins) — these scenes are as starchy and stentorian as the cloudland sequences in superhero films of old. Great actors (Marlon Brando as Jor-El in the 1978 Superman, Laurence Olivier as Zeus in the 1981 Clash of the Titans) tend to go fruity when slumming as fantasy-film deities, and Hopkins nearly surrenders to that campy impulse. The drama flirts so flagrantly with self-parody that one half-expects the actors to burst into their own Mel Brooks lampoon, with Hopkins spritzing, “I just disowned my son and heir, and, boy, is he Thor.”

Given that Thor is a gigantic surfer-god, and Loki slim and black-clad, the film’s platoon of writers (eight are credited) might have gone the familiar Marvel route of turning the malcontent into a troubled hero, a la Peter Parker. But they stick to the Aryan tradition of blond as beautiful and dark as malevolent. The early sequences are also clotted with confounding backstory dialogue — like Thor’s “Have you forgotten all we’ve done together?” — that will have non-Marvelettes thinking they’ve wandered into the middle of another movie. Let’s see: a cold land, frosty mytho-creatures, icy art direction, a woozily pompous atmosphere — could this be an unwished-for sequel to The Last Airbender?

Then you recall that the director is Kenneth Branagh, the actor-director who a quarter-century ago was called the next Olivier — a prophesy that became an albatross. Like Lord Larry, he starred in and directed films of Henry V and Hamlet, but he lacked Olivier’s divine fire; he was more a clever manager than a matinee idol. Between Shakespeares (he also brought Much Ado About Nothing, Love’s Labors Lost and As You Like It to the screen), Branagh directed a morose version of Frankenstein in which he played the scientist to Robert De Niro’s Creature, and a remake of the murder thriller Sleuth, which after much judicious consideration I can call the worst movie of the current millennium. What could he bring to a Marvel comic movie that Spider-Man‘s Sam Raimi or Iron Man‘s Jon Favreau couldn’t?

Turns out Branagh has a deft touch after all; he just waits for the modern scenes to reveal it. Evicted from Asgard, Thor lands in the New Mexico desert, getting promptly creamed by astrophysicist and reckless driver Jane Foster (Natalie Portman, in her sixth film released in six months) and tased by her comic sidekick Darcy Lewis (Kat Dennings). A displaced superhero stranded on Earth, where his special gifts are initially inappropriate, Thor acquires some of the clumsy charm of Jeff Bridges’ interstellar traveler in Starman. The heroic bluster that seemed stilted in Asgard plays as engaging comedy when Thor is confined in a hospital and demands, “How dare you attack the son of Odin!” Clearly, the dude has muscle-management issues. As Jane advises him: “Don’t smash things.”

An action movie is obliged to smash things, just as an action hero has to face outsize adversaries. So Thor contains its share of fights, which are well-staged if video-gamey, and a climactic showdown with a lantern-headed iron giant sent to Earth by Loki. But the central pleasures are in the smaller scenes. The picture finds the right light tone when puny humans, as if in a carnival strength game, attempt to pull Thor’s hammer from the rock where it’s embedded — the Arthurian sword in the stone, transported to the American Southwest. And Branagh brings a tactful warmth to the budding relationship of Thor and Jane. Of the power he learns to harness in his new terrestrial home, he tells her, “Your ancestors called it magic, but you call it science. I come from a land where they are one and the same.” At its best moments, Thor weaves a spot of magic from the complex science of $150-million fantasy-film technology.

Marvel completists will welcome the return of S.H.I.E.L.D. Agent Phil Coulson (Clark Gregg), who popped up in the Iron Man films. And Thor wouldn’t be an official part of the Avengers canon without a visit from Jackson’s Nick Fury, already the most advance-promo’d character in movie history: He doesn’t get his own self-named film until summer 2012, but he showed up in both Iron Man films and will materialize again in this July’s Captain America. I believe Fury was also spotted last weekend at the royal wedding and the White House Correspondents dinner, and he may have been part of the Seal Team Six that took down bin Laden. But we’ll have to wait for the movie version to be sure.

The true god of the project is Stan Lee, who went to work at Marvel (then known as Timely Publications) an astounding 72 years ago, filling inkwells for the artists and soon graduating to writer, editor and chief mythmaker. He and his artists dreamed up Spider-Man, Iron Man, Thor, Fury and the rest of the Avengers team in the space of one year, 1962. Looking spry for 88, Lee has a one-line cameo in the latest film to spring from his lightning-bolt brain. “Did it work?” he asks about I-forget-what. The answer: After a rough start, and when it comes down to Earth, Thor works pretty well.